Bump markdown-exec from 1.7.0 to 1.8.0 in /.config

Bumps [markdown-exec](https://github.com/pawamoy/markdown-exec) from 1.7.0 to 1.8.0.
- [Release notes](https://github.com/pawamoy/markdown-exec/releases)
- [Changelog](https://github.com/pawamoy/markdown-exec/blob/main/CHANGELOG.md)
- [Commits](pawamoy/markdown-exec@1.7.0...1.8.0)

---
updated-dependencies:
- dependency-name: markdown-exec
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.config/requirements.txt

@@ -26,7 +26,7 @@ jinja2==3.1.2
 jsmin==3.0.1
 linkchecker==10.3.0
 markdown==3.5.1
-markdown-exec==1.7.0
+markdown-exec==1.8.0
 markdown-include==0.8.1
 markupsafe==2.1.3
 mergedeep==1.3.4